The present invention relates generally to manual pump mechanisms for dispensing fluid from within a container, and more particularly to pump mechanisms of the type which will dispense the fluid in discrete bursts.
Generally, pump mechanisms of the type to which the present invention relates are mounted upon a container having therein a fluid to be dispensed. The dispensing operation is usually effected by manual downward depression of an actuator member or discharge head containing an outlet orifice through which the fluid is emitted. Repeated depression of the actuator member will result in emission of a discrete burst of fluid each time the actuator is depressed.
Mechanisms of this type are usually structured with a tank which defines within the mechanism a pump chamber within which a quantity of fluid is stored for dispensing. A piston member is arranged in sliding fluid-tight engagement with the tank and depression of the actuator causes the piston to move relative to the tank to eject the liquid contained within the pump chamber. Spring means are ordinarily provided for returning the piston to its original position and movement of the piston under the urging of the spring means will cause a suction effect to be developed within the chamber defined by the tank, and as a result a new quantity of fluid is drawn from the container into the chamber by the suction action of the piston. Thus, during each stroke of the piston, fluid is first ejected and then drawn into the pump chamber.
The fluid is drawn from the container into the pump chamber through an inlet conduit or dip tube which extends from the tank to below the level of fluid within the container, with the dip tube opening at or near the bottom of the container. Fluid is dispensed from the pump chamber through an exhaust conduit in flow communication between the tank and the dispensing orifice in the actuator.
Pump mechanisms of this type require valving means to control opening and closing of the inlet and exhaust conduits communicating with the pump chamber. Usually, when the actuator is depressed and the piston moves to eject fluid from within the pump chamber, the inlet conduit leading into the container must be closed and be maintained closed throughout the exhaust stroke in order to prevent fluid from within the pump chamber from being returned into the container. Such valving mechanisms sometimes tend to be relatively complex in their structure and operation and threfore they may not operate properly causing inadequate operation of the overall pump assembly. Furthermore, such valving mechanisms can substantially increase the cost of production of the pump assembly.
Additionally, problems of leakage such as might occur either through the valving mechanism of the assembly or between the tank and the piston, can give rise to serious operating difficulties.
Pump assemblies of this type are normally manufactured and sold in large quantities. Thus, any slight reduction in the cost of manufacture of such a pump assembly will be translated into significant savings when considered on the basis of the total volume of pumps which may be produced by a mass production facility.
Also, such pump assemblies are usually made from injection molded plastic parts. Accordingly, simplicity in the design of parts of the assembly may make the difference between a product which is inexpensive and simple to manufacture and one which may be literally impossible to produce due either to insurmountable molding problems or excessive manufacturing costs.
Accordingly, the present invention is directed toward provision of an improved pump assembly of the type referred to which will offer certain distinct advantages over structures previously known.